1. Field of the Invention
This invention relates to a laser method for rapid and accurate shaping of optical lenses.
2. Description of Related Art
The use of ablation etching to pattern polymeric material is well known in the art. In U.S. Pat. No. 4,508,749, for example, Brannon et al. discloses an ultraviolet radiation based method for etching patterns in polyimide layers located on integrated circuit substrates, and subsequently depositing an electrical circuit pattern thereover to form electrical interconnections to elements of the integrated circuit. In U.S. Pat. No. 5,236,551, Pan describes a laser-based photoablative etching process for patterning a polymeric film which is subsequently used as a mask for chemical etching of patterns in an underlying metal layer.
Optical lenses produced from polymeric substances such as polycarbonate are well known in the art, and many standard molded lenses are items of commerce. Kohan, in U.S. Pat. No. 5,851,328, and Greshes in U.S. Pat. No. 6,074,579, among others, describe moulding methods for the manufacture of such plastic optical elements. Companies such as Vision-Ease Lens, Inc. of St. Cloud, Minn., and Optical Polymer Research, Inc. of Gainesville, Fla. manufacture polymers and polymer based lenses in a variety of shapes, sizes and optical densities. The lenses are molded for standard patient correction factors such as spherical, aspherical and astigmatic disorders.
Vision care instrumentation for measuring refractive error in a patient are manufactured by several companies such as Bausch and Lomb Vision Care of Rochester, N.Y. and Zeiss Humphrey Systems of Dublin, Calif. These systems have been commercially available for decades.
Instrumentation for measuring refractive corrections for lenses are available from companies such as Neitz Instruments Co. of Tokyo, Japan and Optikos Corporation of Cambridge, Mass. State-of-the-art instrumentation has the ability to measure lens contour to a surface height accuracy of 0.001 mm.
Although correction factors for a patient can be determined with a great deal of accuracy and precision, commercial lenses are provided with standard corrections which do not necessarily fit a given patient""s individuals needs. Custom ground lenses are prohibitively expensive for most patients, as the process of custom grinding requires a highly skilled optician, with experience in lens reshaping. As a result, most patients must accept the standard correction lenses that are available, and consequently do not achieve optimum visual acuity.
Smith, in U.S. Pat. No. 5,350,374 discloses an apparatus and method for performing either photorefractive keratectomy or phototherapeutic keratectomy on the anterior surface of the cornea of the eye using a feedback controlled segmented laser beam.
Neefe, in U.S. Pat. No. 4,307,046 teaches that infrared lasers may be used as the cutting means for shaping a lens. Because the lens is rotated on a spindle in this method, however, the corrected surface is limited to a contour which is concentric with the spindle center.
It is clear from the foregoing analysis that a serious need exists for an economical method for recontouring optical lens surfaces so that correction factors more accurately reflect individual refractive corrections of patients. Such a customized three-dimensional contouring method is not taught in the prior art.
Briefly described, the invention comprises a method for making accurate and precise customized corrections to the surface of an optical lens. An electronic correction contour is generated from a measured refractive correction for a patient, and transferred to the surface of the lens by ablation etching with one or more laser pulses. After each of the laser pulses, the refractive properties of the lens are measured and compared to the electronic contour correction derived from a patient""s refractive correction. The ablation etching is terminated in localized areas where the refractive properties match the electronic correction contour.
The invention may be more fully understood by reference to the following drawings.